Magnetic coupling in EE and EO azido-bridged binuclear copper complexes: Synthesis, structure and magnetic studies

Four azide bridged dinuclear copper(II) complexes, [Cu-2(L-X)(2)(N-3)(2)](ClO4)(2), with L-X = substituted N,N-bis[(3,5-dimethylpyrazole-1-y1)-methyl]benzylamine, [X = H (1), OMe (2), Me (3) and Cl (4)] have been synthesized, out of which complexes 1 and 2 have been characterized structurally. In Complex 1 the two bridging azide ligands have connected the two metal centers in an end-on (EO) fashion with aSP (asymmetric Square Pyramidal) geometry and showed an weak antiferromagnetic interaction (J = -3.34 cm(-1)). On the contrary, in complex 2, the two metal centers have been connected in end-toend (EE) fashion exhibiting moderately strong ferromagnetic interaction (J = +19.7 cm(-1)). Cyclic voltammetric studies performed on all the four complexes show a reasonably good correlations when E-1/2 for (CuCuII)-Cu-II -> (CuCuIII)-Cu-II and (CuCuIII)-Cu-II -> (CuCuIII)-Cu-II oxidations are plotted against sigma (substituent constants) with p = -0.182 (R-2 = 0.92) and 0.684 (R-2 = 0.99) respectively. (C) 2009 Elsevier Ltd. All rights reserved.